This section is intended to provide a background or context to the invention disclosed below. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented, or described. Therefore, unless otherwise explicitly indicated herein, what is described in this section is not prior art to the description in this application, and is not admitted to be prior art by inclusion in this section. Abbreviations that may be found in the specification and/or the drawing figures are defined below at the end of the specification, but prior to the claims.
Mobile broadband traffic continues to increase at an astounding rate. Estimates of the increase are as high as a doubling of the traffic each year for at least the next five years. Heterogeneous networks (HetNets) are being utilized more often to increase traffic capability in congested areas. In these networks, an “overlay” cell (such as a macro cell), with a higher power and a larger coverage area, is complemented with “underlay” cells (such as pico cells) having lower power and smaller coverage areas than the macro cell, but underlying some portion of the macro cell. The lower power cells reduce demands on the macro cell, while, at the same time, providing additional traffic capacity.
A common occurrence when a set of “underlay” cells (or pico cells) is deployed in the coverage area of an “overlay” cell (or macro cell) is that a given pico cell will underlie portions of more than one macro cell, and will then experience interference from more than one macro cell. In such a situation, the amount of interference experienced by the given pico cell from each of the different macro cells may differ. This variation may depend on a number of factors, such as the topology, and the number of UEs in the coverage area of a given pico cell at a given time, but the variation causes the pico cell to have different sensitivities to the ABS muting patterns adopted by different macro cells. At a given time, more ABS from one macro cell may be beneficial to the pico cell, while the pico cell may be insensitive to more ABS from another macro cell. The Almost Blank Subframes (ABS) are used for minimizing the inter-cell interference. Almost Blank Subframes are subframes with reduced transmit power (including no transmission) on some physical channels and/or reduced activity. Using this technique, some cells are muted in certain subframes, so that neighboring cells can have relatively interference-free spectrum.